1. Field of the Invention
This invention relates to tricycloaldehydes. More particularly, the invention relates to a novel tricyclo.alpha.,.beta.-unsaturated aldehyde of the formula (I), ##STR3## wherein the group ##STR4## is attached to the exo side of the norbornane ring at the 8- or 9-position, R represents an alkyl group having 1 to 6 carbon atoms, and the dotted line between carbon 3 and carbon 4 represents a saturated or ethylenically unsaturated bond, and to a process for producing the aldehyde, and further to a perfume composition comprising the aldehyde.
2. Description of the Prior Art
It is known that some tricyclo [5.2.1.0.sup.2,6 ]decane derivatives obtained from endo-dicyclopentadiene are useful as an odorous ingredient for perfume compositions (Japanese Patent Publication No. 49-25340 and No. 51-9014, and Japanese Laid-open Application No. 50-84558 and No. 52-70036).
The present inventors have synthesizd a wide variety of polycyclic compounds similar to sesquiterpenes, diterpenes and adamantanes and have examined their biological activities, and have found that a carbonyl group is introduced regiospecifically and stereospecifically at the 8- and 9-positon on the exo side of a norbornane ring by an oxo reaction of the endo-dicyclopentadiene in the presence of a rhodium catalyst, thereby forming 8- and 9-exo-formyl-endo-tricyclo[5.2.1.0.sup.2,6 ]-deca-3-ene represented by the formulae (IIa) and (IIb) and having an aldehyde group attached to the exo side of the norbornane ring. This finding is disclosed in Synthetic Communications, 6, 199 (1976) and Japanese Laid-open Application No. 52-68168. ##STR5##
As a result of their continued studies concerning the above-mentioned 8-and 9-exo-formyl-endo-tricyclo[5.2.1.0.sup.2,6 ]-deca-3-ene, the inventors have discovered that a tricyclo.alpha.,.beta.-unsaturated aldehyde of the formula (I) can be produced by aldol condensation of the compound of the formula (IIa), or 8-exo-formyl-endo-tricyclo[5.2.1.0.sup.2,6 ]decane obtained by hydrogenating the aldehyde or compound of the formula (IIa) or (IIb), with an aliphatic aldehyde and that the compound of the formula (I) possesses a woody odor. Therefore, perfume compositions may be prepared with the use of the present compound as an odorous ingredient.
Based on this discovery, the present invention has been accomplished.